Polymerised compositions



United States Patent The present invention relates to new polymeric material derived from polymers containing free carboxyl and nitrile groups. It refers in particular to the production of polymeric material with new and improved properties derived from polymers containing free carboxyl and nitrile groups. Q

The copolymerisation of arcyl-onitrile and acrylic acid isknown. It has been suggested that the copolymerisation should be carried out in the temperature range 20-50" C, in aqueous solution saturated with the various monomersemployed. The resulting products are said to be useful for the production of films, foils and fibres. It has also been suggested that a mixture of acrylic acid,

an acrylic ester and/ or acrylic nitrile may be-polymerised together with styrene to form useful products which are soluble in aqueous alkaline solution and may be usedin the preparation of threads, films and coatings.

Weh'ave found that a wide variety of polymers which contain free carboxyl and nitrile groups may be prepared by the ,interpolymerisation of an alpha-beta ethylenically unsaturated carboxylic acid with an alpha-beta ethylenically unsaturated nitrile with the addition of a third copolymerisable compound. i

The interpolymerisation may be effected by the action of heat, ultraviolet light, polymerisation catalysts such asan organic peroxide or other initiators and may take place in the homogeneous phase or in aqueous dispersion. It is preferred that the polymerisation be carried out in the homogeneous phase by subjecting to polymerisation conditions a mixture of the monomeric compounds to be employed. If desired, the monomeric compounds may be dissolved in an inert solvent and the resulting solution subjected to polymerisation conditions. The interpolymerisation may be brought about by subjecting an aqueous emulsion or dispersion of the monomeric compounds to polymerisation conditions, but as stated above, this is not the preferred method because we have found that the polymers produced by this technique are frequently not so readily cross-linked according to the process of the present invention as hereinafter described, as those pro duced by homogeneous phase polymerisation, because one of the reacting monomers may be preferentially solu ble in the aqueous medium with the result that its concentration in the final copolymer is reduced.

It is preferred to carry out the polymerisation in the substantial absence of molecular oxygen gas and this may be most suitably done by carrying out the polymerisation in an inert atmosphere such as nitrogen gas. In this way retardation of the polymerisation reaction and discolouration of the resultant polymer due to oxidation may be avoided.

By alpha-beta ethylenically unsaturated carboxylic aci we mean a monomeric compound which contains the group Examples of such compounds are acrylic acid and its homologues such as alpha-methyl acrylic crotonic, angelic and tiglic acids and its phenyl derivatives such as cinnamic andatropic acids and its halogen derivatives such as alphachlor-acrylic acid. We also include dibasic alpha-beta unsaturated acids such as maleic, fumaric, mesaconic and citraconic acids.

By alpha-beta unsaturated nitrile compounds we mean all those compounds listed above as suitable alpha-beta unsaturated carboxylic acids in'which the carboxyl group or groups have been replaced by nitrile groups.

Asexamples of a third copolymerisable compound" we may mention vinyl hydrocarbons such as butadiene, styrene, alpha methyl styrene and their lower alkyl nuclear homologues, vinyl esters, vinyl ethers, vinyl ketones, N-vinyl compounds and polymerisable allyl compounds. ,Suitable examples of vinyl organic esters include the formate, acetate, propionate, butyrate, stearate and benzoate, suitable vinyl ethers include methyl, ethyl, isopropyl, butyl, phenyl, tolyl, 'napthyl, vinyl and propenyl ethers, while suitable vinyl ketones includes the methyl, ethyl isopropyl and butyl ketones. By N-vinyl compounds is meant compounds having a nitrogen atom to which is attached a vinyl group, suitable examples including N-vinyl urethanes, N-vinyl carbazole, N-vinyl pyrrole, N-vinyl piperidine and N-vinyl pyrrolidone. By polymerisable allyl compounds is meant those polymerisable compounds having an allyl group in the molecule such as esters of allyl alcohol with aliphatic and aromatic carboxylic acids, allyl ethers and allyl substituted aldehydes and ketones and their acetals and ketals. Other suitable polymerisable compounds include the esters of substituted allyl alcohols such as alpha-methallyl, alphaethallyl, alpha-chlorallyl, crotonyl and cinnamyl alcohols and but-l-ene-B-ol and pent-l-ene-3-ol with acids such as formic,acetic, lactic, butyric and glycollic, salicylic, oleic, benzoic and phthalic.

These copolymers of alpha-beta unsaturated carboxylic acids with alpha-beta unsaturated nitriles and the ternary copolymers formed when a third copolymerisable compound is added to the monomeric mixture have a complete range of properties depending on which monomer units are chosen and upon their relative proportions. But it is generally found that these polymers are devoid of the physical properties of a thermoset resin and have low softening points. Further, it is found that they are often readily attacked and dissolved by a wide variety of organic solvents such as acetone, benzene, dioxan, dimethylformamide, ethyl acetate, methylene chloride and tetra hydrofuran.

The object of the present invention is to provide polymerised compositions, derived from the aforementioned polymers which contain free carboxyl and nitrile groups,

which have improved mechanical properties and/or are more resistant to attack by organic solvents.

It has now been discovered that this object may be attained by treating the polymers containing free carboxyl and nitrile groups in such a Way that cross-linking is obtained between the carboxyl and nitrile groups.

It is known that organic acids may be made to react with organic nitriles according to the following equation:

We have made the surprising discovery thatwhen the carboxyl group and the nitrile group are attached to the same polymer chain the interaction of these groups, with Patented Aug. 21, 1956 the consequent formation of intramolecular and intermolecular diacylamino groups may be brought about by the action of heat alone or of heat and pressure on the polymer under conditions which do not destroy the said polymer. The cross-linking afforded in this Way by the formation of the diacylamino groups improves the general mechanical properties of said polymer and/or its resistance to solvent attack thus achieving the aforementioned objects.

Accordingly, the present invention provides a process for the production of new and improved polymerised compositions which comprises heating a polymer containing free carboxyl and nitrile groups attached to the same polymer chain to at least 80 C. with or Without the application of pressure whereby cross-linking by the formation of diacylamino grouping's occurs.

To obtain marked improvements in the nature of the polymer containing the free carboxyl and nitrile groups, it is essential that it should contain a 'sufiicie'nt number of such groups and it is therefore, preferred that the polymers to which the process of the present invention is applied should contain at least 10 mols. per cent of alpha-beta unsaturated carboxylic acid and alpha-beta unsaturated nitrile compound units. It is further preferred that the ratio of the number of free carbonyl groups to free nitrile groups should be in the range of 0.1 to 10 and for polymers containing a low proportion of alphabeta unsaturated carboxylic acid and alpha-beta unsaturated nitrile compound units in their molecular structure the most advantageous results are obtained if they contain substantially equal numbers of free carboxyl and nitrile groups.

The process of the present invention may be carried out in various ways. For instance, the polymers con-'- taining the free carboxyl and nitrile groups may be pressed in a heated positive moulding machine for a time dependent on the temperature and, to a lesser degree, the pressure of working of the machine until the cross-linking has occurred. Generally it is preferred to operate at a temperature in the range 150-200" C. for a reaction period of between 5 and 30 minutes. The pressure of operation is not critical for the process of the present invention so long as it is sufiicient to cause the polymers being treated to flow at the temperature of operation of the machine. Pressures in the range 500 to 7000 lbs. per square inch may suitably be employed. It may be advantageous to mix the polymers with a suitable plasticizer so that the handling and working er the composition may be made more easy. I It is essential, of course, that the plasticizer used should not inhibit the interaction of 'the carboxyl and nitrile groups and it is preferred that, in fact, the plasticizer used should catalyze the reaction as hereinafter described.

It is possible to bring about the cross-linking according to the present invention by the action of heat alone on the polymers containing the free carboxyl and nitrile groups. In this embodiment of the present invention it is necessary to heat the polymer to and maintain 'it at a high temperature for a prolonged period. We have found that the temperature must be at least 80 C. and preferably in the range 100 to 200 C., although any temperature up to the decomposition point of the polymer may be employed. The reaction period may vary from a few minutes up to periods of more than 60 minutes depending on the form of the polymer when subjected to heat and the degree of cross-linking desired. Forinstance when the polymer containing the free earboxyl and nitrile groups contains a high proportion of such groups and is in the form of a fibre, the crosslinking according to the process of the presentinverition maybe brought about by running the fibre through a heated zone in which the period for which the fibre is heated is only a few minutes. It will of course be appreciated that the time necessary to achieve a substantial change in the physical properties of the polymer to be treated by the cross-linking reaction of the present invention will vary greatly with its constitution and consequently those polymers with low proportions of carboxyl and/or nitrile groups will require high reaction temperatures or long reaction times, or both, whereas those polymers with high proportions of carboxyl and/ or nitrile groups will only require the milder reaction coniQ e We have further found that the reaction of free carboxyl groups with free nitrile groups attached to the same polymer chain may be catalysed by acidic catalysts. For instance, acidic inorganic compounds such as ammonium chloride and ammonium phosphate, Friedel- Crafts type catalysts such as aluminum chloride and zinc chloride and weakly acidic organic compounds such as the monoesters of phth'alic acid, and strongly acidic compounds such as p-toluene sulphonic acid, beta-camphorylsulphonic acid, trichloracetic acid and phosphoric acid may be used. As mentioned above many of these catalyst's, such as, for instance, c'etostearyl hydrogen pathslate, have some plasticising action upon the polymer to be treated according to the process of the present invehtion and, therefore, their use may be advantageous.

According to a modification of the present invention the new and improved polymerised compositions may be obtained directly by carrying out the polymerisation of the alpha-beta unsaturated carboxylic acid and the alphabeta unsaturated nitrile with the addition of a third copolyr'nerisible compound under such conditions that the polymer chains containing the free carboxyl and nitrile groups which are initially formed react further and become cross-linked due to the formation of diacylamino groupings. I I

Previously the inter-polymerisation of unsaturated acids and nitriles of the type described above has been car- 'ried out at temperatures below C. and usually below 50 'C. The low temperatures have been preferred because it has been found generally in the art of polymeri s'atio'n that as the temperature of polymerisation is increased the molecular size of the resulting polymer is reduced with the consequent increase in its vulnerability to solvent attack and deterioration in its mechanical properties. I

We have found, however, that if the inter-polymerisa tion of an alpha-beta unsaturated carboxylic acid with an alpha-beta unsaturated nitrile with or without the addition of a third copolyme'ris'able compound be carried out under special conditions, notably at temperatures above 100 'C., it results in new and improved polymeri'sed compositions in which cross-linking has occurred due to the formation of dia'cylamino groupings. The polymers formed in this way have improved resistance to solvents and improved mechanical properties over the corres onding polymers formed by polymerisation of the same monomers under conditions heretofore employed, i. e. at temperatures below 100 C. It will be appreciated that the optimum conditions whereby the improved products of the present invention are produced will vary with the nature a'nd 'relative 'concentration of the monomers e'rnployed. "For instance, we have found that where the concentration'of the 'third copolymerisable compound is above 60 mol's. per cent of the whole reaction mixture, the polymerisation is best carried out at temperatures well above 100 "C1, i. e. at temperatures up 'to 200 "C. On the other hand, when the concentration of the third copolyrnerisa'ble compound is reduced below 60 'in'ols'. per cent, i. e. the concentration of the unsaturated carboxylic acid and nitrile is increased, it may be possible to produce the improved products of the present inventionb'ycar'rying 'out the polymerisation at lower temperatures, i. e. temperatures near 100 C.

Another factor, which may be varied to bring about the special conditions necessary for the production of the improved polymerised compositions according to the fiibd fitiation of the present invention, is the duration of .5 the polymerisation period. For instance, the temperature of. the polymerisation process may be decreased if the, time allowed for the polymerisation is increased.

As has been mentioned before, the reaction of carboxyl groups with nitrile groups is catalysed by the addition of any of the aforementioned catalysts and accordingly any of them may be added to the monomeric mixture which is to be polymerised according to the modification of the present invention provided that the catalyst chosen is compatible with the monomer mixture and does not inhibit the polymerisation thereof.

The polymerised compositions producedaccording to the above modification of the present invention may still contain some free carboxyl and nitrile groups which have not been converted into diacylamino groupings and, of course, these polymers may be further cross-linked according to any of the processes hereinbefore described.

The polymerised compositions of the present invention may becompounded or mixed with compounds such as pigments, dyes, fillers, stabilisers and the like, if so desired either before or after the cross linking reaction. It is however, essential that the added compounds should not inhibit the formation of the diacylamino groups according to the process of the present invention if the addition of these compounds is to be made before the cross-linking reaction is carried out.

One advantage of the process of the present invention is that no water or other volatile low molecular weight product is evolved during the cross-linkingand consequently the produced polymerised compositions have good mechanical and electrical properties and find a wide variety of uses.

.-For instance not only can they be used for the production of moulded articles with improved physical characteristics, but also some of the cross-linked polymerised compositions of the present invention may be used as lacquers or adhesives. For this use of ;the polymerised compositions of the present invention it is often most advantageous to apply the polymer containing the free carboxyl and nitrile groups to the surfaces to be lacquered or-glued and then carry out the cross-linking reaction on the thin film of polymerthus obtained.

The following examples are given to illustrate the production of various polymers, containing freecarboxyl and nitrile groups attached to the same polymer chain and their subsequent improvement according to the process of the present invention. Examples 4 and 5 illustrate the modification of the present invention wherein the production and the cross-linking 'of the polymers are carried out at one and the same time. The parts referred to are by weight.

Example 1 A ternary copolymer was. obtained by: the single phase polymerisation of a mixture of 87.5 parts of styrene, 7.2 parts of acrylic acid and 5.3 parts of acrylonitrile at 80 C. for 192 hours in an atmosphere of nitrogen. "The resulting polymer was dissolved in a 1:1 benzene/dioxan mixture, precipitated from solution and washed with.

ethanol to give polymer A. V

To a 10 gram sample of polymer A was added 0.02

gram of cetostearyl hydrogen phthalate in 20 mls.'of ethanol. partial esterification of phthalic acid with an approximate- This hydrogen phthalate ester was made by the 1y equimolecular commercial mixture of cetyl and stearyl alcohols. After mixing the solvent was removed and the resultant polymer was pressed in a 2" diameter circular positive mould for 15 minutes at 180 C. at 4000 lbs/in. to form a disc of cross-linked polymer c0ntaining diacylamino groupings (sample B).

Another cross-linked sample disc was prepared by treating a 10 gram sample of polymer A witha solution of 0.02 gram of ammonium chloride in 20 mls. of dilute aqueous dioxan. The solvent was removed and the polymer pressed as before to give sample C.

The relative resistance to attack by ethyl acetate of 6 these three samples was then determined by adding mls. of ethyl acetate to 10gram samples. Sample A dissolved readily to give a clear solution, while sample B was swollen, and finally disintegrated to form a stringy gel. Sample C. was swollen to an opaque gel which retained the shape of the unswollen specimen.

Example 2 w./v.) but gave a very stiff opalescent gel.

Example 3 A further ternary copolymer was prepared by emulsion polymerisation under nitrogen of 100 parts of styrene, acrylic acid and acrylonitrile in the same molar ratio as in Example 2 emulsified in 200 parts of 2% w./v. aqueous sodium lauryl sulphate solution containing 0.1 partof isopropyl benzene hydroperoxide. The polymerisation was carried out for 40.5 hours at 50 C. to give 84.7-parts of polymer. This polymer with benzene gave a 10% w./v. solution with no sign of gelation.

10 parts of the polymer was intimately mixed with 0.02 part of p-toluene sulphonic acid and the resulting mixture pressed under the same conditions as in Examples 1 and 2, to give a moulding which with 88 parts of benzene (10% w./v.) gave a viscous opalescent gelatinous solution.

Example 4 A mixture of. styrene, acrylic acid and acrylonitrile in the same proportions as in Example 1 was polymerised in homogeneous phase under nitrogen for 47 hours at C. The resultant cross-linked polymer was swollen but not dissolved by dioxan, ultimately the polymer disintegrating to form a gel. This is in complete contrast to the ternary copolymer prepared according to' Examples 1, 2 and 3 which were readily soluble in dioxan.

Example 5 The direct production of cross-linked polymers by single phase polymerisation is illustrated by the examples tabulated below in which a 10:1:1 molar styrenezacr'ylic acidzacrylonitrile mixture was used and in which the time and temperature of the polymerisation were varied as shown. The degree of cross-linking is evidenced by solubility or swelling in dioxan (10% w./v.) according to the following scheme.

Not cross-linked Completely soluble no gelation. Slightly cross-linked Highly swollen to form a soft mobile gel. Cross linked Swollen to form stitf gel-retaining shape of original specimen.

Heating Cycle Appearance of Degree of Sample polymer cross-linking Time (Hrs.) Temp.

1 90 at 80 }Milky white and cross-linked. followed by 75 at 130 hard. 2 9a 80 do Do followed by 4 at-" l 3 2 160 Almost clear, very Not cross- B e yellow, linked.

rittle. 4 18 160 Opaleseent, Slightly faintly yellow, crossbrittle. linked. 5 18 160 Pele yellow, alcross-linked. most clear,

rather soft.

7 In sample above 0.1% w./w. p-toluene sulphonic acid was added to the monomers.

Example 6 8 The copolymer was soluble in acetone, dimethyl-formamide, dioxan, ethyl acetate and tetrahydrofuran. After positive moulding under the conditions described in Example 1, it formed stringy gelatinous dispersions in these The various ternary copolymers of styrene, acrylic 5 olv g acid and acrylonitrile shown in the following table, were prepared by sealing the monomer mixtures in glass tubes Examp 9 under nitrogen and heating the mixtures for a given time in an oil bath thermostatically controlled at the required 3 3 12: g s g j i g g is g ggg c i? temperature. Benzoyl peroxide was added as polymerf g elmxu 3 6 isation catalyst in certain of the examples and the relamm p t 1 e i t b 1 tive proportions of the monomers employed was eX- fi i f one an gg, pressed in molar parts by weight. The c'opolymers thus i m ig po ig t or a t predueea were then cross-linked by subjecting them to a th e resulmg F g 2 wa f pressure of 4000 lbs. persquare inch for 15 minutes at 15 1 e cope an fee mm re a temperature of 180 c.1111 a 2" circular positive mould. $3 g i ea th The solubility characteristics of the various 'copolymers d f p g l P081 we q i t e niannet before and after the cross-linking reaction were comtxamp i u onset pared in solvents such as acetone, dioxa'n, ethyl acetate, u a i g a: van 2 lolxan F dirnethylformamide and tetrahydrofuran and the results gs y Sm a y varymg 6 con moms 0 Po ymensa' ll t ble are Shown f0 Gwmg a h I 7 If the acetone is replaced by cyclohe'xane, with which fndicates that the copolymer was Q the monomers are all miscible, the polymer is precipitated lIldlCateS that the p if was hlghly SW01- as polymerisation proceeds and may be separated by v t0 form a 80ft, mobile 2 filtration. The resulting polymer may be cross-linked in I.. indicates that the copolymer was swollen to 5 the m manner form a stiff gel retaining the shape of the Example 10 original specimen. It will be seen from the table below that the solubiiities of A cop'o y f ryli acid nd ryl n triie w s methe various copolymers shown are reduced by the posipared y the em111S111 P01Ymer1$at10fl of 3 1111710116 tive moulding process thus indicating that cross-linking f 08 p r of potassium persulphate, 0.3 part of ha oc urred, sodium metabisulphite, 20 parts of acrylonitrile and 2.7 E l 7 parts of acrylic acid in 400 parts of distilled water under xamp e an atmosphere of nitrogen at 36 C. for 2 /3 hours. After The 'copolyrner d of Example 6 was dry-spun into standing overnight the unreacted monomers were removed fibres from a 20% solutiOn in dioxan. After stretching, by steam stripping and the polymer slurry filtered and the fibres were passed slowly through a zone heated to washed to give 18.2 parts of a very pale yellow powder. 130 C. in an atmosphere of nitrogen. The heat-treated The polymer had a nitrogen content of 22.6% which corfibres showed increased tensile strength and were insoluresponds to 85.6% acrylonitrile unit's. ble in dioxan and in dimethylformamide although the 40 The eopolymer wa readily oluble i dimethyl-formuntreated fibres were soluble in both these solvents. amide and in a 1:1 dimethylformamide-acetone mixture.

Exam 1e 8 Fibres were prepared by wet spinning a 10% solution p of the polymer in 1:1 acetone-dimethylformamide into an A tetnary Q g fprt pared addglg fat 1? ueous coagulating bath. The fibres after heating for :3; gg g g i of sg g ii gz 0 fi gg g i a short time at 160 C. in an atmosphere of nitrogen propyl hydroperoxide slowly over a period of 1% hours were no longer Soluble m dlmethylformamlde' to 500 parts of a 2 w./v. aqueous sodium lauryl sul- Example 11 phate solution containing a further 0.15 part of lsopropylbenzene hydroperoxide and preheated to 80 C. The Terpolymers were prepared uslng a number of alterna- Monoiner Mixture Heating cycle c gelaltlzgiitsyncs Catalyst, Appearance of Sample percent Polymer Styrene, Acrylic Acrylo- .Time, Temp, byweight Before After Positive Mols. Acid, nitrlle, Hours *0. Positive Moulding Mols. Mols. Moulding 2 1 1 118 100 Pale yellow I. Lessswollen.

transparent. 3 1 1 118 100 g 8 n o 5 i i i3? 53 312:. e r. 1 1 1 115 0.1 Pale yellow G I.

bubbled. 2 1 -1 1115 e0 0. 1 d S -I. 2 1 1 240 '60 Paleyellow G I. '2 1 1 24 5 '60 o 05 31 1 s I '2 '1 1 "212 "60 0:05 III G- I: 1 1 1 24 60 0.05 Opaiescent G 1.

yellow.

whole operation was carried out under reflux with vigortive monomer systems, as below; in each case a molar ous stirring in an atmosphere of nitrogen, and the temratio of 1 moi;alpha-beta-unsaturated acid: 1 mol. alphaperature was maintained at 80i2 C. throughout the beta unsaturated nitriles: 2 mols. third monomer was addition of the monomers. V employed.

Immediately the addition was completed, unchanged 'Poiymeris'ations were carried out at 80 C. with the mon'o'me'rs were removed by steam stripping and the readdition of 0.05% w./w. on total monomers of benzoyl sultin latex precipitated with alcohol to yield 65 parts peroxide. The time of polymerisation was varied accordof copolymer.

ing to the monomer'system used.

1 Alpha-beta Alpha-beta Unsatu- Unsaturated rated Nitrile Third Monomer Acid a Maleic acid--- Acrylonitrlle Styrene. b Acrylic acid Orotononitrlle Do. do.- Do. :1 Do.

Methyl methacrylate. Vinyl ethyl ether. Vinyl chloride.

Ethyl citraconate. Ethyl chloromaleate. Vinyl crotonate. Ethyl acryiate.

The various terpolymers produced above were crosslinked by pressing samples between platerns heated at 180 C. for minutes under a pressure of 1000 lbs. per square inch. The polymers a, b, vc, d, e, h, i, k and l were initially all soluble in acetone but became insoluble after the cross-linking reaction. Copolymers f, g, j, m, and n were initially all highly swollen by acetone but after cross-linking they were substantially unaifected by the solvent.

Example 12 Samples of ethyl acrylate, acrylonitrile, acrylic acid terpolymers were prepared by copolymerisation in single phase 35% solutions in acetone and used as thermosetting adhesives for duralumin. V

Close-contact joints having an overlap of 1" x A" were prepared from 4 /2" X 1' pieces of duralumin thick, by spreading the acetone solution, allowing the solvent to evaporate and pressing according to the follow- 7 ing schedule.

Open assembly time 10 mins. 20 C. Pressing temperature 180 C. Pressing time mins. Pressing pressure 130 lbs/sq. 1n.

Mean shear strength figures (after cooling) shown in the following table are similar to the strengths obtained with commercial phenolic adhesives for aluminum alloys.

Acrylo- Ethyl Mean shear Acrylic acid nitrile Acrylate strength in (Molar parts) (Molar (Molar lbsigoer parts) parts) 1" x lap Example 13 Copolymers were prepared by refluxing the following mixtures until polymerisation was complete, n an atmosphere of nitrogen (quantity in parts by weight).

Oopolymer No. a b v c 1.0 Acetone 1,300 2,100 1,580

Although the process of the present invention has been described with particular reference to those polymerscon g taining free carboxyl and nitrile groups derived from the copolymerisation of. alpha-beta unsaturated-:carboxylic acids and nitriles' as hereinbefore defined, it is within the scope of the present inventionto apply the process of *the'present invention to other polymers containing free carboxyl and nitrile groups whereby improved polymer'ised compositions may be formed due to the formation of di-acylamino groups. For instance, polymers containing free carboxyl and nitrile groups may be obtained by the polymerisation of a monomer containing both free carboxyl and nitrile groups. Polymers containing free carboxyl and nitrile groups may also be produced as a result of polycondensation reactions such as, for instance, the condensation of a polyhydric alcohol containing free nitrile groups with excess of a polybasic acid. It is further possible to produce polymers. containing free carboxyl and nitrile groups by. copolymerising a monomer containing a nitrile group with one containing a potential carboxylic acid group which may be released after polymerisation. For instance, polyacrylonitrile may be partially hydrolysed to form a polymer containing both free carboxyl and nitrile groups.

We claim:

1. A process for the production of a cross-linked polymerized composition which comprises interpolymerizing an alpha-beta ethylenically unsaturated carboxylic acid with an alpha-beta ethylenically unsaturated nitrile in the presence of a third copolymerizable compound to produce a ternary interpolymer containing at least 10 moles per cent of alpha-beta unsaturated carboxylic acid and alphabeta unsaturated nitrile units, the ratio of the number of free carboxyl groups to free nitrile groups being 1:1, and thereafter maintaining the interpolymer at a temperature of -200 C. until cross-linking by the formation of diacylamino groupings has occurred.

2. A process as claimed in claim 1 wherein the ternary interpolymer contains at least 60 moles per cent of units obtained from the polymerization of the third copolymerizable compound.

3. A process as set forth in claim 1, wherein the interpolymerisation is carried out in the substantial absence of molecular oxygen.

4. A process as set forth in claim 1, wherein the cross-linking reaction is brought about with the aid of an acidic catalyst.

5. A process as set forth in claim 4, wherein the acidic catalyst employed is an organic acid which is a plasticiser for the polymer containing the free carboxyl and nitrile groups.

' 6. A process as set forth in claim 1, wherein the crosslinking reaction is brought about during a molding operation at a temperature in the range to 200 C. and for a reaction period of between 5 and 30 minutes.

7. A process as set forth in claim 1, wherein the crosslinking reaction is brought about by passing a fibre of the polymer containing the free carboxyl and nitrile groups through a heated zone.

8. A process as set forth in claim 1, wherein the crosslinking reaction is brought about in a thin film of the polymer containing free carboxyl and nitrile groups on a surface to be lacquered or glued.

9. A cross-linked polymerised composition containing diacylamino groupings derived from a polymer containing free carboxyl and nitrile groups according to the process of claim 1.

10. A cross-linked polymerised composition containing diacylamino groupings derived from a ternary interpolymer of styrene, acrylic acid and acrylonitrile according to the process of claim 1.

11. A cross-linked polymerised composition containing diacylamino groupings derived from a ternary interpolymer of ethyl acrylate, acrylic acid and acrylonitrile ac cording to the process of claim 1.

11 12 12. A process as set forth in claim 1 wherein the cross- 2,445,042 Silverman July 13, 1948 linking reaction is brought about with cetostearyl hydro- 2,456,360 Arnold Dec. 14, I948 gen'phtheilate as acidic catalyst. 2,592,248 Coover et a1. Apr. 8, 1952 References Cited in the fil e of this patent 5 UNITED STATES PATENTS 2,436,926 Jacobson Mar. 2, 1948 

1. A PROCESS FOR THE PRODUCTION OF A CROSS-LINKED POLYMERIZED COMPOSITION WHICH COMPRISES INTERPOLYMERIZING AN ALPHA-BETA ETHYLENICALLY UNSATURATED CARBOXYLIC ACID WITH AN ALPHA-BETA ETHYLENICALLY UNSATURATED NITRILE IN THE PRESENCE OF A THIRD COPOLYMERIZABLE COMPOUND TO PRODUCE A TERNARY INTERPOLYMER CONTAINING AT LEAST 10 MOLES PER CENT OF ALPHA-BETA UNSATURATED CARBOXYLIC ACID AND NAPHABETA UNSATURATED NITRILE UNITS, THE RATIO OF THE NUMBER OF FREE CARBOXYL GROUPS TO FREE NITRILE GROUPS BEING 1:1, AND THEREAFTER MAINTAINING THE INTERPOLYMER AT A TEMPERATURE OF 100-200* C. UNTIL CROSS-LINKING BY THE FORMATION OF DIACYLAMINO GROUPINGS HAS OCCURRED. 